PreferenceUIHostingController. Adds hiding home indicator and deferring system edge gestures to SwiftUI. (Don't work at the same time but I think that's normal?)

PreferenceUIHostingController.swift

extension View {
    /// Controls the application's preferred home indicator auto-hiding when this view is shown.
    func prefersHomeIndicatorAutoHidden(_ value: Bool) -> some View {
        preference(key: PreferenceUIHostingController.PrefersHomeIndicatorAutoHiddenPreferenceKey.self, value: value)
    }
    
    /// Controls the application's preferred screen edges deferring system gestures when this view is shown. Default is UIRectEdgeNone.
    func edgesDeferringSystemGestures(_ edge: UIRectEdge) -> some View {
        preference(key: PreferenceUIHostingController.PreferredScreenEdgesDeferringSystemGesturesPreferenceKey.self, value: edge)
    }
}

class PreferenceUIHostingController: UIHostingController<AnyView> {
    init<V: View>(wrappedView: V) {
        weak var weakSelf: PreferenceUIHostingController?
        super.init(rootView: AnyView(wrappedView
            .onPreferenceChange(PrefersHomeIndicatorAutoHiddenPreferenceKey.self) {
                weakSelf?._prefersHomeIndicatorAutoHidden = $0
            }
            .onPreferenceChange(PreferredScreenEdgesDeferringSystemGesturesPreferenceKey.self) {
                weakSelf?._preferredScreenEdgesDeferringSystemGestures = $0
            }
        ))
        weakSelf = self
    }

    @objc required dynamic init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
    }
    
    // MARK: Prefers Home Indicator Auto Hidden
    
    fileprivate struct PrefersHomeIndicatorAutoHiddenPreferenceKey: PreferenceKey {
        typealias Value = Bool
        
        static var defaultValue: Value = false
        
        static func reduce(value: inout Value, nextValue: () -> Value) {
            value = nextValue() || value
        }
    }
    
    private var _prefersHomeIndicatorAutoHidden = false {
        didSet { setNeedsUpdateOfHomeIndicatorAutoHidden() }
    }
    override var prefersHomeIndicatorAutoHidden: Bool {
        _prefersHomeIndicatorAutoHidden
    }
    
    // MARK: Preferred Screen Edges Deferring SystemGestures
    
    fileprivate struct PreferredScreenEdgesDeferringSystemGesturesPreferenceKey: PreferenceKey {
        typealias Value = UIRectEdge
        
        static var defaultValue: Value = []
        
        static func reduce(value: inout Value, nextValue: () -> Value) {
            value.formUnion(nextValue())
        }
    }
    
    private var _preferredScreenEdgesDeferringSystemGestures: UIRectEdge = [] {
        didSet { setNeedsUpdateOfScreenEdgesDeferringSystemGestures() }
    }
    override var preferredScreenEdgesDeferringSystemGestures: UIRectEdge {
        _preferredScreenEdgesDeferringSystemGestures
    }
}

PreferenceUIHostingControllerSwizzling.swift

/// If you are unable to access window.rootViewController this is a method using swizzling 
struct PreferenceUIHostingControllerView<Wrapped: View>: UIViewControllerRepresentable {
    init(@ViewBuilder wrappedView: @escaping () -> Wrapped) {
        _ = UIViewController.preferenceSwizzling
        self.wrappedView = wrappedView
    }
    
    var wrappedView: () -> Wrapped
    
    func makeUIViewController(context: Context) -> PreferenceUIHostingController {
        PreferenceUIHostingController(wrappedView: wrappedView())
    }
    
    func updateUIViewController(_ uiViewController: PreferenceUIHostingController, context: Context) {}
}

import SwizzleSwift // I have a fork of this for SPM (Amzd/SwizzleSwift)

extension UIViewController {
    static var preferenceSwizzling: Void = {
        Swizzle(UIViewController.self) {
            #selector(getter: childForScreenEdgesDeferringSystemGestures) <-> #selector(childForScreenEdgesDeferringSystemGestures_Amzd)
            #selector(getter: childForHomeIndicatorAutoHidden) <-> #selector(childForHomeIndicatorAutoHidden_Amzd)
        }
    }()
}

extension UIViewController {
    @objc func childForScreenEdgesDeferringSystemGestures_Amzd() -> UIViewController? {
        if self is PreferenceUIHostingController {
            // dont continue searching
            return nil
        } else {
            return search()
        }
    }
    @objc func childForHomeIndicatorAutoHidden_Amzd() -> UIViewController? {
        if self is PreferenceUIHostingController {
            // dont continue searching
            return nil
        } else {
            return search()
        }
    }
    
    private func search() -> PreferenceUIHostingController? {
        if let result = children.compactMap({ $0 as? PreferenceUIHostingController }).first {
            return result
        }
        
        for child in children {
            if let result = child.search() {
                return result
            }
        }
        
        return nil
    }
}

Can't seem to work for me either on SwiftUI. It compiles fine but nothing happens. Any help would be great thanks !

Did you guys replace UIHostingController with PreferenceUIHostingController in the SceneDelegate/AppDelegate? @lezone @amrmarzouk

Hi, does this work with SwiftUI 2.0? Having trouble getting it to go. Likely operator error but thought I'd check.

Can't seem to work for me either on SwiftUI. It compiles fine but nothing happens. Any help would be great thanks !

Did you do this in your SceneDelegate? The functions return a new SwiftUI View, so you can't use them inside the view itself

// Create the SwiftUI view that provides the window contents.
let contentView = ContentView().prefersHomeIndicatorAutoHidden(true)

// Use a UIHostingController as window root view controller.
if let windowScene = scene as? UIWindowScene {
  let window = UIWindow(windowScene: windowScene)
  
  window.rootViewController = PreferenceUIHostingController(wrappedView: contentView)
      
  self.window = window
  window.makeKeyAndVisible()
}

@NoahKamara you CAN use them inside your views? It’s just a modifier like any other modifier

@NoahKamara you CAN use them inside your views? It’s just a modifier like any other modifier

In that case it unfortunately doesn't work for me. Do you have a working example for me to take a look at?

struct Example: View {
    @State var deferSystemGestures = false
    
    var body: some View {
        VStack {
            Toggle("Toggle System Gesture", isOn: $deferSystemGestures)
        }.edgesDeferringSystemGestures(deferSystemGestures ? .all : [])
    }
}

Just confirmed this works on iOS 14 too.

Thanks, works great if I have a SceneDelegate. Is it possible to make it work with @UIApplicationDelegateAdaptor?

I have the same issue as @patrick ^. I am using the new SwiftUI App Life Cycle, so no Scene/App Delegates.

I think I got it to work.

MainApp.swift

import SwiftUI
import Foundation

@main
struct MainApp: App {  
 @UIApplicationDelegateAdaptor(MyAppDelegate.self) var appDelegate
    init() {
    }
    var body: some Scene {
        WindowGroup{
         //   MainView()   // created this in MySceneDelegate below instead
        }
    }
}

then in MyAppDelegate.swift

import UIKit

class MyAppDelegate: NSObject, UIApplicationDelegate {
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
        // Override point for customization after application launch.
        return true
    }

    // MARK: UISceneSession Lifecycle

    func application(_ application: UIApplication, configurationForConnecting connectingSceneSession: UISceneSession, options: UIScene.ConnectionOptions) -> UISceneConfiguration {
        // Called when a new scene session is being created.
        // Use this method to select a configuration to create the new scene with.
        
        let config = UISceneConfiguration(name: "My Scene Delegate", sessionRole: connectingSceneSession.role)
        config.delegateClass = MySceneDelegate.self
        return config
    }

    func application(_ application: UIApplication, didDiscardSceneSessions sceneSessions: Set<UISceneSession>) {
        // Called when the user discards a scene session.
        // If any sessions were discarded while the application was not running, this will be called shortly after application:didFinishLaunchingWithOptions.
        // Use this method to release any resources that were specific to the discarded scenes, as they will not return.
    }
}

and in MySceneDelegate

import SwiftUI
//
class MySceneDelegate: UIResponder, UIWindowSceneDelegate {
    
    var window: UIWindow?


    func scene(_ scene: UIScene, willConnectTo session: UISceneSession, options connectionOptions: UIScene.ConnectionOptions) {
        // Use this method to optionally configure and attach the UIWindow `window` to the provided UIWindowScene `scene`.
        // If using a storyboard, the `window` property will automatically be initialized and attached to the scene.
        // This delegate does not imply the connecting scene or session are new (see `application:configurationForConnectingSceneSession` instead).

        // Create the SwiftUI view that provides the window contents.
        let contentView = MainView()

        // Use a UIHostingController as window root view controller.
        if let windowScene = scene as? UIWindowScene {
            let window = UIWindow(windowScene: windowScene)
            window.rootViewController = PreferenceUIHostingController(wrappedView: contentView)
            self.window = window
            window.makeKeyAndVisible()
        }
    }

    func sceneDidDisconnect(_ scene: UIScene) {
        // Called as the scene is being released by the system.
        // This occurs shortly after the scene enters the background, or when its session is discarded.
        // Release any resources associated with this scene that can be re-created the next time the scene connects.
        // The scene may re-connect later, as its session was not necessarily discarded (see `application:didDiscardSceneSessions` instead).
    }

    func sceneDidBecomeActive(_ scene: UIScene) {
        // Called when the scene has moved from an inactive state to an active state.
        // Use this method to restart any tasks that were paused (or not yet started) when the scene was inactive.
    }

    func sceneWillResignActive(_ scene: UIScene) {
        // Called when the scene will move from an active state to an inactive state.
        // This may occur due to temporary interruptions (ex. an incoming phone call).
    }

    func sceneWillEnterForeground(_ scene: UIScene) {
        // Called as the scene transitions from the background to the foreground.
        // Use this method to undo the changes made on entering the background.
    }

    func sceneDidEnterBackground(_ scene: UIScene) {
        // Called as the scene transitions from the foreground to the background.
        // Use this method to save data, release shared resources, and store enough scene-specific state information
        // to restore the scene back to its current state.
    }
    
}

and finally my MainView.swift

import SwiftUI
struct MainView: View {
    @State var deferSystemGestures = false
    var body: some View {
        VStack {
            Toggle("Toggle System Gesture", isOn: $deferSystemGestures)
        }.edgesDeferringSystemGestures(deferSystemGestures ? .all : [])
    }
}

https://www.google.nl/search?q=how+to+use+uiviewcontroller+in+swiftui&ie=UTF-8&oe=UTF-8&hl=en-gb&client=safari

Thanks for the Google suggestion. I tried, failed, and posted the code and a stack overflow question about it: https://stackoverflow.com/questions/67474403/defer-system-edge-gestures-in-only-some-view-controllers-swiftui

Ah okay so I missed this detail https://developer.apple.com/documentation/uikit/uiviewcontroller/2887511-childforscreenedgesdeferringsyst

Apparently the system only asks the first UIViewController and if that vc doesn't return a child that the system should ask too then that's it.

You could introspect a UIView > get its window > check if the rootViewController is a PreferenceUIHostingController > if not wrap the root in a PreferenceUIHostingController.

This assumes SwiftUI doesn't change the rootViewController after the initial change and is not very safe but I can't think of a better way.

So I wrote a fix that makes this work with SwiftUI only using swizzling. It might be possible to do without swizzling but this works.

I added it as second file to this gist.

Use by wrapping your views with PreferenceUIHostingControllerView

PreferenceUIHostingControllerView {
    ExampleView()
}

@PatrikTegelberg @amrmarzouk @lezone

Hi. In the second file, I think the second 'swizzle' should be:
#selector(getter: childForHomeIndicatorAutoHidden) <-> #selector(childForHomeIndicatorAutoHidden_Amzd)

I have tested it with this change using the ios14 SwiftUI life cycle and it seems to work well.

You are correct @smithi01

I updated the gist

I am most grateful for this code - thank you. I dim a view in my app if it is idle for a while and use my own .dimIfIdle() modifier along with your .prefersHomeIndicatorAutoHidden(timer.idle). 'timer' is my StateObject. I simply code the view that all this happens in with "PreferenceUIHostingControllerView { PanelView() }". This is wonderful because it let me move away from AppDelegate and SceneDelegate.

Has anybody had any luck adapting this to the iOS 16 life cycle? This no longer works for iOS 16 and while .persistentSystemOverlays(.hidden) is available, this is more preferential.

@LePips Do you have any more info on why this doesn't work on iOS 16? is there a new api for deferring system gestures in UIKit? as it should just use that right? or does the swizzle no longer work?

I do not have an idea why they don't work, the swizzled methods just aren't called. Most specifically, I am looking at the home indicator but I strongly assume this would also apply to all other methods.

Here is a minimal example that works for iOS 15 but not iOS 16:

Example

The commented out appDelegate is explained below.

@main
struct PreferenceHostingDevApp: App {
    
//    @UIApplicationDelegateAdaptor(MyAppDelegate.self)
//    var appDelegate
    
    var body: some Scene {
        WindowGroup {
            PreferenceUIHostingControllerView {
                ContentView()
            }
        }
    }
}

struct ContentView: View {
    
    @State
    private var showSecondView: Bool = false
    
    var body: some View {
        ZStack {
            
            VStack {
                Image(systemName: "globe")
                    .imageScale(.large)
                    .foregroundColor(.accentColor)
                Text("Hello, world!")
                
                Button {
                    showSecondView = true
                } label: {
                    Text("Present")
                }
            }
        }
        .ignoresSafeArea()
        .fullScreenCover(isPresented: $showSecondView) {
            SecondView(showSecondView: $showSecondView)
        }
    }
}

struct SecondView: View {
    
    @Binding
    var showSecondView: Bool
    
    var body: some View {
        VStack {
            Text("Hello There")
            
            Button {
                showSecondView = false
            } label: {
                Text("Dismiss")
            }
        }
        .prefersHomeIndicatorAutoHidden(true)
    }
}

Other things attempted:

• setting the scene window root view controller (via the appDelegate)
• create another solution that uses a proxy ObservableObject which will manually call the update method on the view controller
• wrapping SecondView in a PreferenceUIHostingControllerView

@LePips Hmm, is it possible that the preference key doesn’t forward from a presented view? Have you tried without the presented view?

If you mean trying to hide the home indicator on ContentView, that does work